What do I do if I don't have anyone to write my letters of recommendation for undergraduate research programs? I'm currently a second year student in maths and I want to apply to some REUs but I haven't made any remarkable relationships with my profs or anyone in the department. As well, I've just been an average student, just As and Bs, so I don't have anything exceptional to show for my attendance in my profs' classes. Thus, if anyone has any advice on what I can do for LORs, I'd appreciate it. 

Additional info: I am doing research in my university, just not in maths, it's in pedagogy, but my supervisors don't know what's going on in my classes. I also have emailed this great prof I had last year once this year and have asked her for an LOR already, but I don't know how wiling she will be to give me another one since it's been a couple of months since we've last talked.
Just go talk directly to people who might be interested in working with you. They won't be far away, anyway. You have to build up a reputation to get LoRs, and given your current status you just won't have it.