Transistor identification
Could you please help find an alternative to it?


Without knowing the complete schematic, it's impossible to find an alternative for it, as different component will have different characteristics and may affect the system greatly. It's better to just stick with the known one you provided before.




  I am having trouble identifying it


I don't know if you have read this or not, but if you haven't, it may have some useful tips for you.



Lets find it!

Sometimes, looking on online store may work if its stock is available. Otherwise, the result may be excluded from its search menu. Thus, the google cache may be your best friend. Such as using these keyword:

X04V site:aliexpress.com 
XO4V site:aliexpress.com


Also, online forums or non-English sites may also help you, I've found on google this Chinese store here and I've found its discussion here.

It's true that finding SMD Marking can be a labyrinth adventures.
So try to look at SMD Marking database on the internet first.

And it's common for several attempts to be failed. I've failed to find it on here here and here. Those packages listed are not SOT23 from your picture. Fortunately, I've found it here with only one correct SOT23 package.

By verifying on the manufacture Alpha &amp; Omega Semiconductor Inc. (AOS) product page, here.

This is screenshot from Marking pdf that the company provide.



It's seems legit that this X04V 1A is AO3400A N-Channel MOSFET 30V 5.7A@Vgs=10V.

Reasons:


The IC on your picture package is SOT-23
X indicates its product type.
If you take a look on A03400 (notice without "A" letter at the end) product page here on its datasheet. There are negligible differences on its spec, only \$\mathrm{R_{DS(ON)}}\$ and \$\mathrm{I_D}\$. And it's only differs by one significant figure. Also the marking of its product is "A" and not "X". I don't know in the first place why AOS build those two almost identical IC with both Full Production status.
0 indicates it's AO3400A or AO3400AL
AO3400AL is the Lead-Free version. Although its not stated in the datasheet, but from other Alpha Omega Semiconductor datasheets such as here, I can see the pattern and conclude that it's the Lead-Free version. Read more about Lead-Free from other Q&amp;A on this site here or here.
4 indicates the Week code
V indicates the assembly location code (probably private internal information)
1A indicates the assembly lot code (probably private internal information)
At first, it may makes sense to think that 1A is the current rating of a MOSFET or linear regulator. But I highly doubt it in this case, because of the previous clues.


  https://eesemi.com/assyglossary.htm 
  lot - a group of similarly-processed semiconductor devices, usually from the same production run, treated as a homogeneous population
  
  https://www.svmi.com/glossary-terms-semiconductor/ 
  Lot: Wafers of similar sizes and characteristics placed together in a shipment.





Where to buy it?

You may search on your local reputable supplier, or you can search it on AliExpress for cheap here, but I won't guarantee that it is counterfeit or not. Also you may notice at AliExpress the marking will vary such as A09T, it's the one without letter A before. For 3400 marking, it's from different manufacture, CYStech Electronics Corp from Taiwan which is MTN3400N3, which also has nearly identical spec. By the way, A0XX and 3400 are nearly identical with X0XX so you can also buy those instead.

Warning! A1XX, X1XX, and 3401 are P-Channel MOSFET, make sure you do not buy that.

For reputable online supplier I'm unable it to find on Farnell and Mouser doesn't seems to supply from AOS (Mouser supplier page). But I found it on Digi-Key here for 0.45 USD (without shipping rates). 

I can only find AO3400A on Digi-Key (which is available in stock) and unable to find it for the other two before.



Conclusions

You could imagine we could find nearly three identical SMD component from thorough searching process with such distinct marking information. That's why I stated earlier, this could be labyrinth adventures. I hope it will help you and someone else reading this in the future.

I recommend you to buy its replacement from the Digi-Key that I've linked before or your local reputable supplier.