You can alway have a barrel pick up a .30 cal barrel and have it machined down like I did if not you could be waiting months if not.
I had 25 cal fx barrel machined down to a 20" and proper diameter and worked with Donny FL to piece together his Leshiy shroud worked out great. Now it was a spare barrel I had laying around that was never going to get used so clearly I made a project out of it for the Leshiy. Though, for you unless you have a spare 30 cal barrel there are few good 30 cal barrels out there you can pick up and have machined down to what ever length and diameter to have fit. It is pretty simple too retro a barrel for a Leshiy.
I have dealt a lot with Joost from luchtbuks.com, very trustworthy guy. And very knowledgable of all things edgun. Mail or call him, he will be able to help you I think.