Travel grant for undergraduate researcher for attending conference
There are several strategies for this in addition to the usual ones outlined previously. I assume you are in CS/IS/IT from your profile. Your primary costs are conference registration fees, air fare and living expenses.


If its a top conference, it will have student volunteer positions. For instance, this and this. This defrays cost of registration (free) and some of your living expenses (food and some cost of living). Apply for it immediately.
You mention that you are getting some travel grant from the conference. Thats a good thing. Keep it for airfare.
If its a ACM/IEEE conference, it will be sponsored by a SIG. SIGs have their own funding. For instance, see this and this. If you are an ACM/IEEE member then you can apply for these funds which are independent of conferences.
Sometimes, in limited ways, industrial research labs and other government labs have funding. Search for and apply for these. For instance, see this , this and especially this.


I was once a poor student and had to make use of multiple sources of funding to go to conferences. You can also do it ! Basically, apply for everything that you find and see. Of course, the best way is to simply ask another co-author or someone actually visiting the conference to present the paper.

Another way is to just pay the registration fee (which is comparatively less). That way your paper is still indexed in the ACM DL or IEEE Xplore etc.