There have been Sten bits and pieces in the last few auctions. Prices have been insane. A bolt and barrel could exceed $1000.
Making a barrel would certainly be an option. A piece of .35 caliber barrel and a buddy with a lathe and chamber reamer would be needed. If the blank diameter is too small for a one piece barrel, a barrel can be made in two pieces, as many original Mk. II barrels were fabricated. Pretty basic shop operations.