Fitting chain protection is notoriously difficult and depends on bike details. The options include placing an outer disk, and there following the directives of
dedhed and
GeezyRider, and/or mounting a chainguard that extends backwards over the chain. A good source for both is AliExpress but with long delivery times. Also a lot of browsing, looking at details, is required. Given low prices, long delivery times and high chances for mismatch, it is presumably advisable to order two or more solutions, hoping that at least one will work.