I find MSA to be a complete pain in the a$$ for availability of parts, they say its in stock but then when you are ready to order (and combine all shipping in one go) they tell you that its out of stock and should be 4-6 weeks away

They can also be difficult to get hold of, pretty much every time i have used their main email address (sales or info@ or something like that) they never get back to me.
Last time i ended up spamming every address i could find until i got a salesmembers address.
For reference, jon(at)motorsportauto.com has been very helpful for me in the past.
As for Black dragon, i havent dealt with them, though i did buy a pair of inner quarter window rubbers (2 seater) and a rear windscreen seal off Tim (RB30X)
He says that he bought them from Black dragon. I was very happy with the quality and fit of them.
Just my 2 cents