Yep, its a Levys, but its not custom made, I bought the exact same strap from Sound Control in Newcastle about 3 years ago for 40 quid. Dont know if they are still making them mind.
Go to the Levy's website and look under 'Garment Leather Straps', you will see the MSS2 there, although the new logo is slightly different to the old one on Bri's strap.
PS the bottleneck holder on Brians strap is simply a piece of leather which he has taped on himself.