Mark,
Any machine shop or hobby engineer should be able to make you pair of strikers in less than a hour's labour.For material you could use a pair of capscrews (allen bolts) without having to heat treat at all.There are many schools of thought on the making of strikers, some people harden, some don't.
My thoughts are that the purpose of a striker is similar to that of a metal punch, which are hardened and tempered so that is what I do.