That's not how PS Now works. For the VIta, it was a 100% streaming service that streams directly from Sony's servers. You can't "inject" a game into their servers, that makes 0 sense. Not to mention PS Now isn't even available for the Vita anymore, it was discontinued last year, so you can't even access the service from the Vita anymore.
You can use Remote Play, however, if you have a PS3/PS4, that you can use to stream most games to your Vita. For the PS3, it does need to have CFW so you can add more games to the Remote Play compatibility list, but for the PS4 any game you own that supports Remote Play should work just fine.
If you don't have a PS3/PS4, you're shit out of luck.