Yeah, there are plenty of smaller species of loach. Clown loaches are significantly larger than any of the other common species.
Good ones to look at are:
botia kubotai
yoyo loaches/botia almorhae
zebra loaches/ botia striata
botia histronica (harder to find)
botia rostrata (harder to find)
Y. Sidthimunki
Y. nigrolineata (harder to find)
None of them really get more than about 4-5 inches. They all have a similar body shape to Clowns and are relatively peaceful.