12" Silent Runner! The flying saucer is way too small! It will be very frustrating for your hamster. Our last Syrian was very large and heavy and managed to break a couple of wheels by thundering away on them so not surprised the saucer is rattling with even a small syrian on it!
They do better with an upright wheel as they run better but it can be nice to have a saucer as well but all syrians need the 12" saucer. If you have a Zoozone though, the 12" Silent Runner won't fit I think - it's 35cm tall on it's stand and I seem to remember the maximum height of the Zoozone 2 is quoted as 36 cm or 37cm but internally it's slightly less. It might fit in the central if you measure the internal height but you need a good 1 cm of clearance so it doesn't catch and rub. The alternative would be a senior wodent wheel which is good for a Syrian and both easily available. With that you may need something heavy on the base/stand under the substrate as they can move around otherwise - eg a ceramic tile sitting on the base under the substrate to stabilize it.
This is the Silent Runner. Exotic Nutrition are also the cheapest place to buy wodent wheels I believe.
https://www.exoticnutrition.com/Prod...r)__43673.aspx
Senior wodent wheel - I think this would be the better option for the Zoozone - it will definitely fit (unless it's the smaller Zoozone 1). Not classed as silent but they are usually pretty silent. And an ideal size for a Syrian hamster. Unless your Syrian grows very large then you might need a deeper wheel. The wodent wheel is quite compact at 7cm deep.
https://www.exoticnutrition.com/Prod...-11__WW11.aspx
If it's the Zoozone 1 you have then only an 8" or 9" wheel would fit.