I get my SCBA tanks filled at the firehouse and mine have the cga 347 valve. Same as what our local fire fighters use. It's also the most common valve on 4500 psi firefighter tanks. I would ask them which fitting they run that way you can call and get exactly what you need the first time. My cousin works at one in another county and they use a totally different valve so I would need an adapter to fill there.
I use the bottom adapter option at my fire house as I was able to assemble one for around 30 bucks. It works well.
Before you spend money on hardware, confirm for sure, that they will fill for you, and that they can fill to 4500psi! Many (I suspect a majority) fire departments will not fill tanks, for liability or other reasons.
Lawyers don't have me "whooped" into anything. They have the city/county fire depts whooped into not filling SCBA tanks for private citizens. I have to resort to paying a whopping $3.95 for a 4500psi fill at my local scuba shop.
Rajod,I found this Crosman adapter, model: FAH007, for $28.77 on Amazon:You could also get it from Crosman and see if it's cheaper with the AGNATION promo code on Friday with free shipping.Taso