Classic Army ISSC Mk22

[AMari67]

Good Morning/Afternoon, 

 So I found my old Classic Army ISSC Mk22 in my garage and it looks like I lost the entire hopup unit for the gun. I’m looking for a new hopup unit to install into this gun, but don’t really know what would be compatible with it.

I don’t have the user guide to the gun, nor I can find schematics or online manuals. 
It also looks like this gun is a discontinued model as well. Internally it’s a V2 gearbox and the nozzle is pretty long, unfortunately that’s all I know since I’m not really good with gearbox internals.
I’m stuck thinking it’s between a M4 style unit or a Scar style unit. 
If anyone has/knows what style of unit would work with this gun. I would gladly appreciate it. 

[colinjallen]

It is the same hop as they use in their Scar-L: https://www.titano-store.com/en/c/airsoft-c28617/rifles-internal-spare-parts-c28847/hop-up-c28962/hop-up-chamber-scar-l-classic-army-p433m-p909683