My99 uk classic airbox resonator delete snorkel
 

Is there anyone still making a snorkel for the standard airbox to replace the resonator?

Why do you want to remove/mod the snorkel?

I want retain the standard airbox but fit high flow filter and replace the resonator with an aftermarket snorkel

OK, snorkle and resonator are two different things. The snorkle is before the air box and the resonator is after.
Which do you want to modify?

Not on an my99 turbo 2000 it's not, the resonator is in the wing

The item in the inner wing is the snorkle, so called as is helps prevent the ingress of water to the inlet. The deletation of this item has no gains what so ever.
The resonator is a black oval affair under the bonnet, sat between the air box and the inlet. Deletion of this item will increase induction noise and 'possibly' incease air flow.

not on the later classics, they don't have the resonator inline, its contained on the link pipe that goes to the airbox in the wing and several companies used to produce a replacement for this pipe that deleted the resonator