Go borrow some different grips and see if they fit.
There are some grips that work or can be made to work with some shimming.
I tried a CYMA AK74U grip on mine and I'm pretty sure with some shimming it would fit.
I'd like to put some LCT grips on mine, but I don't have any to check with.
***also, report back. I'm interested to know if real sword supplies them and what they charge. I'd like to get some backups. Real sword might also be able to tell you what brands they're compatible with.
RS Type 56-1 & RS Type 97B & KWA M11A1 w/steel kit
KJ M1911A1 & KSC G19 + AI Grenade