Air tank for FWB P70

Hi. I am going to go/try dark!!!

what is the best and/or most economical way to fill the cylinder on a Feinwerkbau P70 match rifle?

I am wanting a tank, do not mind it being steel (if a High pressure works) or used. Unsure if the 3500psi steel tanks can fill this airguns’ cylinder (full at 200bar/2900psi)? I have done some research on tanks but it is all still Greek to me. My simple mind says to buy a used steel HP tank (100cf) from the local dive shop, with a valve. 

The tank removes from the rifle, and attaches to a small brass adapter that I believe is of the DIN variety. Gauge on end of cylinder. 

I see a lot of carbon cylinder setups for 750$+. Is there a less expensive way to keep this rifle aired up?
 
Thank you for the response. I had even read the thread you linked to. 

I visited the Dalmatian fire website too. Didn’t seem really user friendly so I kept on moving. Maybe I should call them and see what’s available along with costs once shipping is calculated. 

Whats the obvious reason for CF over steel? Weight? Doesn’t bother me. Higher pressure? That is saying 3500psi isn’t enough, or that I will be able to get more fills?

If Dalmatian fire is the way to go, what is the oldest tank date one should consider buying?