I did mine both sides and couldn’t believe how easy it was - I should have done it years ago !
The Bearmach MUC 1005 is actually rubber - and isn’t a channel - but has a flat side and a curved side, so it folds to sit inside.
I bought two, but then realised there is enough length in one piece for both windows.....
So it’s £1.75 plus VAT - the issue is postage; 6.25 plus VAT from Bearmach direct, though you can roll other purchases up into that.