Asura Dynamics has been a company that dedicates in providing modern solutions to the AK platform, and recently they have produced the Asura Dynamics SRW Style Folding Stock that turns your standard folding ak stock (PP-19-01, AKS74U, AK105, AKS74, AK74mn) into a folding buffer tube that accepts military spec m4 / AR-15 buttstocks that can also be folded.
This would adapt to AK AEG / GBBR receivers.
*Note the buffer tube would not lock to the side of the receiver when folded.
Disclaimer: All aftermarket upgrade parts require necessary skill or modification to install and assemble, please consult with your airsoft technician if needed.