Most of my rimfire red dots are just 1 inch tubes with 1 inch rimfire rings and I have a 30mm as well.
Some are made specifically for rimfire but then that's all you can use them on and for the most part they are cheaper red dots which may or may not be good for you.
You can also get a rimfire to weaver rail adaptor if you really like a certain red dot that only comes with a weaver attachment.
I like UltraDot red dots myself and I've gotten them in the past no problem from rimefire sports and they offer free shipping to Canada.
Someone up here should start selling Ultra Dot's but for some reason no one is....
http://www.rimfiresports.com/merchant.mv?Screen=CTGY&Store_Code=RSC&Category_Code=OR
For the adapter rails check them out here, BSquare ,BKL, and Leapers and maybe some others as well... they are a bit bulkier and will raise your red dot but it would allow you to go with a micro style red dot..
http://www.dlairgun.com/Mounts.html