There's a few different ones available; htc desire holster - Google Product Search Take your pick

I have the official HTC pull tab case. But then I have no desire (pun intended ) to clip it to my belt

 

PDair make very nice Desire cases. I have the horizontal holster which I think is a better orientation if you actually intend to keep it on the belt clip but they do vertical as well. try expansys or just google "PDair Desire Case"

 

I can highly recommend the Piel Frama Magnum case. It comes with a strong belt clip.
It is a beautiful, strong well made case.

Their customer support is excellent as well.

Expensive but worth it.

 

Have one for my T5 too, going strong after many years.

The flip gives it much protection. I feel safe without a screen protector.

 

I think you need one of these

Leather holsters - mobile phone cases - UK stock available online

 

isnt this a tad overboard?? if i ever saw a wannabe / yuppie accessory then this must be it.

 

not sure if this is a response to my suggestion but if so PDair do do book style but I was referring to these 2 which are not:

PDair Leather Case for HTC Desire (Vertical Pouch Type Belt Clip Included, Black) #3BHTDEV01 - eXpansys UK
PDair Leather Case for HTC Desire (Horizontal Pouch Type, Black) #3BHTDEP01 - eXpansys UK

I have the horizontal on and it is the best made case I have ever had.

 

This is what i use and i an vary happy with it. My phone has fallen already once without the slightest problem, the camera lens depresses and protected from scratching . No need to remove the phone at all , just flip open the case like a clam shell.

Leather Case Cover, 2 Screen Protector for HTC Desire on eBay (end time 25-Aug-10 22:27:48 BST)