I looked at converting my 14 speed road bike to 1x7 with a 38T chainring and adding a bashguard. Most of the store bought bashguards I saw were at least $25 and for a max size 38T to 44T chainring. For that money you can buy another 42T ring. If you want a chainguard for a 52T ring you may have to make one from another big ring and grind/cut/file the teeth off.