This is my remix of Jesses side release buckle over on Thingiverse:

https://www.thingiverse.com/thing:312961

The male part now fits either way, also it is scaled down quite a bit from the original and the edges are rounded a little for a nice touch. 

The buckle is for 25 mm straps. You can scale it up or down widthwise a bit to fit your strap. I tried scaling it down 80% widthwise and this fits 20 mm straps nicely.

The strength of the part is quite untested, so do not use it in "life or death" applications. For low load applications it has worked great so far.

Print instructions

Use PETG.

Supports included, male part is printed laying flat, female part is printed standing up.