Late Peninsular War Portuguese and Spanish, who were supplied with British kit (no lace on the front, though). Portuguese shakos earlier on were very similar to the Belgic shakos.
And I have converted some to Brunswick Oels, although that involved a head swap (French style shako) and work on the shako plumes.
And there were some foreign troops in British service (Sicilians. I think?) who wore this same uniform.
Or, you could just give them to me!
![Big Grin :-D](./images/smilies/icon_biggrin.gif)
(Joking - have enough...)