This is my own take on a Picatinny rail riser for airsoft. This was designed for M2 hex screws and nuts, specifically socket head cap screws like these: https://www.amazon.com/gp/product/B082XRX17Z/ref=ppx_yo_dt_b_asin_title_o03_s01?ie=UTF8&th=1 You'll need 2 M2*10 screws and 2 nuts.
This is designed to fit standard Picatinny, and it fits on all 3 of my airsoft guns from various manufacturers. However, since the tolerances are pretty tight, they might need slight filing or sanding to fit. I didn't deal with any issues, however. I reccomend PLA Tough, but other filaments will work. The riser in the pictures is black PLA Basic and it works just fine.
When NOT in use on a picatinny rail, please DO NOT fully tighten the screws. This riser is designed to form fit to the picatinny rail, but if tightened off of rail it may bend the M2 screws or break the plastic.
Happy airsofting! This is my first foray into Picatinny so I'm very proud of this model.