I would say here personally. The selection, quality and prices are varied in Sharm itself. Most of the beachside dive places or boat trip organisers will hire them to you as well BUT I'd rather know that the snorkels only been inside my mouth

I bought a very good set several years ago from JJB sports for about £23 which have served me very well.

Get a good mask over here, go to a diving shop and they will make sure it fits properly. Do not buy a cheap mask it will only leak and fog up all the time.
Any cheap snorkel will do if you don't mind blowing out a bit of water, or selse pend a few quid motre and get one with a vent and drain.
Fins also need to fit - though needn't be expensive.

I bought a Bodyglove snorkel and mask set about 9 years ago and it has served me well on 8 visits to Egypt to far, amd going for the 9th in 3 weeks time and considering buying a new set as a treat but Im after Bodyglove as I find them so comfy. The snorkel and mask set when I bought them 9 years back were £20 so I would expect to pay about £25-£30 for the same kit now. Hope this helps!

Hi

Loads of information about snorkeling in this existing topic - http://www.holidaytruths.co.uk/viewtopic.php?f=32&t=190