I'd clean up the threads as best as you can so that another barrel adjuster will thread in & hope for the best.
Another option if the existing threads strip completely out or are drilled out, is to remove the plastic sleeve & spring & install a small nut on the replacement adjuster threads so that adjustability can be restored. The mechanic at your LBS likely has one rattling around the top of his tool box.
Or, do as above minus the small nut I mentioned & use an inline adjuster at some convenient place along the housing run. Up by the shifter is pretty common. Down by the frame headtube/toptube is subject to twisting forces with every steering correction & is less likely to stay well adjusted for long. (Ask me how I know.)
I see you have a Deore rear derailleur. Do you have a matching flat bar shifter? If it has a barrel adjuster, all others are reduntant, anyway. Screw the derailleur one all the way in & fugghedaboutit.
