You can buy this for $25:
This light-weight aluminium splined wrench is designed to fit Scubapro low pressure hoses and most models of jam nuts on second stage regulators. Not only does it provide a good fit for both the plastic (part # 11.755.120) and the metal (part # 11.250.106 and # 11.263.106) versions of the part...
scuba-clinic-tools.com
But, the actual ScubaPro tool has a lot more uses. And it's still nice and compact to fit in a reg bag.
If you're a dive pro and going to be spending years working on these things, why not buy the right tool and be done? I bought one of these after my ScubaPro class. Do I use it much? No. Am I glad to have it when I do need it? Yes.
This is the ScubaPro Universal Tool for Scuba Diving RegulatorsFeatures: This combination spline, cap, and pin spanner tool does it all. It is designed for both the repair bench and travel tool kit. The hose spline wrench slides firmly over Scubapro swivel hose ends and will not mar the chrome...
www.houseofscuba.com