Seems you have some general problems with chains ...
That's bad and the first case mentioned here in the forum.
As you mention the valve, I guess the valve hit the piston. First of all, find the cause of this. My wild guess is a failed chain tensioner was the reason.
It's important to find all the parts gone bad, otherwise you'll have trouble again soon afterwards. Have a look at the "Werkstatthandbuch". Is the cam shaft ok? Valve seat? Valve guide? Rod? Piston? Chain? Chain guides? Chain tensioner? ...
You should be able to get the parts from Beta. As the parts are genuine Suzuki parts anyway, purchasing them from Suzuki is usually ~20% or so cheaper. Unfortunately, there are several different DR200 years and some different models, so I cannot tell you for sure which parts will fit. Maybe a Suzuki dealer is able to help you.
An example parts catalog of a DR200SE 2013:
www.bike-parts-...DR200SE-L3-E24-/4281
(again: I'm not sure if the parts are identical!)