There's probably several ways to do and it all depends on your requirements i.e.
Layer 3 or Layer 2?
PoE or non PoE?
A quick example of stacked configuration would be:
1 x WS-C3750X-12S-S
1 x WS-C3750X-24T-S
That would give you two switches with the following port capacity:
12 x SFP (Can take a varity of CISCO SFP's (1000 Base-T - Copper or 1000-BaseSX - Fiber). - Switch 1.
24 x 10/100/1000 Copper Gigabit + Optional expansion slot.
Without looking at expensive chassis soluitions there isn't a Cisco switch that combines 12 SFP & 12 Copper interfaces in the same unit. You have to mix & match units or mix & match line-cards in a bigger unit.