Bobby Shew names a mute made in Sweden (how ironic, given your name) in the following words:
There is a company in Sweden that makes the Dizzy Gillespie model
mutes which, when you can find them, are worth purchasing although
very expensive. The cup in this set is made of a white plastic and
separates into two pieces, one of which looks like a straight mute and
which could be used as one, and another piece which is similar to a
plunger which snaps over the end of the straight to form a cup. It has
a surprisingly good sound for being plastic. It lacks the hard,
brittle quality which makes the metal mute undesirable,
People at thetrumpetherald seem to think the brand name is Ullven:
They don't seem to be in business anymore, and I am not even sure that that is the model Gillespie actually uses.
Bobby Shew seems to like the Humes & Berg MIC-A-MUTE,
which is the same as the basic cup with a rubber ring around the edge
of the cup to control the seal or space near the bell of the horn.
This mute also has a soft fuzzy material covering the inside of the
cup area, the purpose of which is to soften the "wooden" hardness of
the sound of the regular cup.
I believe this could be the best you can aim for?