you may build your own, you need just a glass marble from eBay from 3 to 120 $ , a stainless steel road, a round cabinet handle, a 1/4 diamante bit and an universal glue from Home Depot. some time, some imagination probably a bit more expensive then a purchased one but will be "home made" and for sure you will be more pride with.
i build for myself two, one black with white mix for grass and one red with gold insertions for sand.
all the best