Can I replace loose ball bearings with caged ball bearings in my hub?
Yes, you can get caged bearings to go in the hub. RJ The Bike Guy seems to have several YouTube how-to videos (hint: they have to go the right way round)

No, they are not better than loose balls. Caged balls are spaced out evenly, but have fewer balls in total which means fewer balls sharing the load, so they are said to wear out quicker. 

With loose balls, you need to leave a little bit of room for them to move, so you’d put in one less than fills the whole cup. Given that caged sets typically have seven balls, if you put nine in loose then you’ll still have more bearings (better) than using a caged set. I.e. if you’re concerned about the space between balls, 9 loose is still preferable to 7 caged. 

Some front hubs can take 10 balls, it depends on the design. You need to figure out which size your hub requires - presumably the majority of your balls are still the original size. If you can measure that then figuring out, or asking the LBS, or asking here in another question with photos, how many to put in, should get the hub running smoothly again.