Most older Russian mig-29 airframes are quite heavily worn out, though.Russia can just simply do the same here with regards to MiG-29 variants.
There is some opportunity to assemble parts which are still around since 1993 (in particular, India looked at them before 2022), but overall it isn't as simple as it may sound.
mig-29m2/mig-35 airframe is available(the latter is desirable as it's quite new and thorough upgrade - maybe even able to even out 1st gen kf-21), but any reasonable quality satellite footage will immediately tell them apart from the vanilla airframes.