The hamster heaven cage is actually about 38cm high - the 50cm height thing is misleading as it includes the height of the penthouse. But it's still high enough to fit a 27cm to 30cm wheel in. How big is your syrian? Average, large? If she's average sized then the 28cm Trixie wheel might be ok too. It's plastic and a bit lightweight so would probably need something to hold the base down. The wood wheel would need plastikoting (waterproofing). They're good wheels though, but it would need checking over carefully for any rough bits or splinters and then painting with the plastikote paint.
Pets at home don't seem to have much else of a choice online - not sure about in store, but you can order the Trixie wheel from Amazon or Zooplus here.
http://www.amazon.co.uk/Trixie-Exerc...s=Trixie+Wheel
It's only £8 at Zooplus but then there's postage on top. £11 at Amazon with free postage.
Small Pet Exercise Wheel | Free P&P on orders £29+ at zooplus!
Wodent wheels are also good and sturdier than the Trixie wheel but you can only get those online at two places and they're out of stock at both. If you wanted one though I could sell you the one I just bought and was about to return as I need a bigger wheel. I paid £15 plus £4.50 odd postage, but you can have it for £15 and I'll pay the postage if you want it. If not I'll return it. You can order them from Germany but it might be easier to get a Trixie wheel. I wouldn't recommend the Trixie one if you have a really big heavy syrian though.
Here are some pics of Wodent Wheels
Wodent Wheel Description