Good idea. I am very interested in this. Made a-php once a couple of years ago following a procedure similar to this one:
https://pastebin.com/d6qNceQH. MDPV should not differ that much, both starting with a substituted ketone like propiophenone or hexiophenone derivative like caprophenone which one may have to synthesize depending on availability, then the addition of a pyrrolidine ring through a condensation rxn with the ketone intermediate. MDPV has a 3,4-methylenedioxyphenyl ring, which is not present in a-php, that should require an additional step for incorporating this ring. Reduction of a substituted phenyl-2-propanone (P2P) like 3,4-methylenedioxyohenyl-2-propanone and then the introduction of the pyrrolidine ring via reductive amination or another nitrogen substitution reaction would be the 2 key steps if these reagents can be sourced.
If anyone in the US is interested in bringing this chem back to markets then shoot me a PM and we will make a session groupchat where we help each other research this synth, maybe find a good writeup by someone who's done it, and look for sourcing on the reagents.