Hi!
I fly the Katana quite a lot a Redhill, and the club there (Cubair) produces its own checklist for their aircraft based on the information in the POH.
A generic version of the Katana POH (for both the -A1 and the -C1) is available in book form written by Ed Helmick - a quick search for "Diamond Katana" in your favourite online bookstore should be successful. This book includes checklists which are pretty good, although not quite the same as the ones Cubair produces (and sells).
Surecheck also have a checklist for the Katana in a handy flip-over binding, although I never really got on with this one as it is a little biased towards the American system (AROW documents, etc).
One thing to watch for on the Katana (DA20-A1 only) is that as the mixture control is automatic, there is no Idle-Cutoff during engine shutdown - you do turn the key just like in a car. However there is a BIG gotcha in this - you MUST let the exhaust cool by running the engine at idle for at least 30 seconds before killing the "mags" otherwise the unburnt fuel expelled while the engine slows and stops can ignite in the exhaust stack and has been known to blow the exhaust muffler. This is not easily spotted during the pre-flight due to the restricted visibility - the Katana has a very tightly cowled engine and only a small inspection opening to check the oil and coolant levels. I have once found a Katana where this had happened and the only way I spotted it was that the coolant bottle had actually melted. I dread to thing what could have happened had the muffler cracked on the other side, away from the inspection port, but right next to the battery...
Safe flying - I hope you like the Katana as much as I do.
Cheers,
MD.