Maybe these or this. Dunno about the availability but you can try your luck at Lazada?

I can't decide which one to get now! https://www.amazon.com/gp/product/B0748S3GXG/

There are a lot of different controllers. You can get them really cheap in China but then you'll have to wait a couple of months.

I bought myself a pair of these:

https://www.amazon.com/8Bitdo-SF30-Controller-Windows-macOS-Android/dp/B0748S3GXG/ref=mp_s_a_1_7?dchild=1&keywords=retropie+controller&qid=1596883801&sprefix=retropi&sr=8-7

i would say these https://www.amazon.com/8Bitdo-SF30-Controller-Windows-macOS-Android/dp/B0748S3GXG?th=1 but the d pad on them SUCK, they can be fixed but thats a bit involved, i have a video on how to do it. but if you can wait they have these coming out, but no one knows how the d pads will be on them. https://images.idgesg.net/images/article/2018/06/dscf6917-100761444-orig.jpg