Telect's smallest panel that supports both circuit breakers and GMT fuses is the 350CB06, which is 3RU in height.  The 350CB06 supports up to 6 breakers per side as well as 5 GMT fuses and has an input rating of 350 AMP. 

Telect does offer a 1RU circuit breaker only panel (009-7000-0104) with 4 breaker positions and an assortment of 1RU GMT fuse only panels with 5, 10, or 20 GMT fuse positions depending on input loading.