There are HTPC casings locally available, such as Antec NSK series and Fusion series ... it's a little bit pricey, but serves the purpose.
Just one note on HTPC's, there was an earlier post mentioning that what matters is what's inside the case - this is only partly true for HTPC requirements due to following reasons -
1. If you are installing the HTPC on an AV rack, most standard PC casing (even the mini-casing) may not fit an AV rack - AV rack shelves are usually limited to less than 10-inch in height.
2. You do not really need a very powerful PC for an HTPC - what you need is a motherboard or a graphics card with HD video acceleration capability and a big HDD capacity to store your contents - not much processing power is required