Need Retaliator 7KG or 9KG spring

Hi all,

Hoping someone can help me source a Retaliator spring upgrade in the USA.  

I ordered the 9KG spring with the Sig Sauer MCX kit from Worker but they failed to include that spring in the order.  It happens, I still love them!

As you know it's gonna take 3 weeks to get one from HK and my son and I are looking at the gun with the nice new plunger, breech, metal catch, reinforced sled, and no spring.  I did try the stock spring but it is way too weak to move the new plunger assembly, even greased up.

Sorry if this is a lame first post.

Thanks

Tanner Cortes