Replacement carb for Irvine 20

[Eleck Rider]

Hello, I have a question. Having spent a long time chasing the tune on my Marauder's Irvine 20 I tried some experiments to find out why it has been so inconsistent - and I'm not even looking for optimum power here, I just want the damn thing to idle reliably.

After trying different fuels and plugs I tried a Just Engines carb which made a significant difference. Trouble is it's a plane carb and doesn't sit comfortably in a buggy.

It seems that the Irvine jetstream carbs I have are perhaps a bit tired. Does anybody have any suggestions of a modern equivalent? Thanks.