Right your options are - buy a 3000psi bottle, and smartparts on/off tap and you can use the reg on your gun at present.
3000psi doesnt give you as many shots as 4500psi though.
The other option is buy a second hand 4500psi air system for about £200, and buy a eclipse frm for about £30 and mount your reg from the bottom on to your marker. (confusing i know)
Or buy a new 4500psi Max-flow and bottle for £350ish
Hope this makes sense, ill through in some site words to make you feel at home.
Punters, smokers, petrol can, van.