Well like I say it would be very easy to fabricate one with a small aluminium sheet.
Whatever you do will very likely be a temporary measure because I doubt you will like the way the bike will run.
The caps I think you are referring to on Ali Express are hollow - so you again would need to fabricate an 'end cap' to cover it?
The attached photo is of something that I have seen used previously but am uncertain of where to get them in your location.
I have had a few bits from Ali Express previously and found them good value.
Would be very interested to see how you got on.
If you were in the UK I have a few bits of old exhaust that you could have had to experiment with.