I'm sure some have seen this, but i know they were hard to get a while back when Franks was moving.
https://hvccycle.net/fork-tubes-yamaha-rd-250-350-1973-1975-351-23124-50-00/?mc_cid=ee6f369573&mc_eid=fa6d6d5c4e
https://hvccycle.net/fork-tubes-yamaha-rd-250-350-1973-1975-351-23124-50-00/?mc_cid=ee6f369573&mc_eid=fa6d6d5c4e