Without the vertical spit, there is absolutley no way one can make gyros to equal doing it that way. A horizontal spit deosn't work because the ground lamb spice mixture will not adhere. The stuff you can purchase frozen or otherwise is junk!
But, one can make a passable product at home. You need top quality lamb. not pre ground. Grind yourself using whatever spice mixture you like. Pre-cook a bit of the mixture and taste, noting that you always require more seasoning than you think, sort of like a pate.
Put into bread loaf pans and cook in your oven. Cool and slice. Now, you need a griddle and olive oil as well as home made pita bread and sauce, all of which you can make much better yourself than any you can purchase.
Heat up your griddle, coat with olive oil and brown your sliced gyros. Works better than anything out side of Greek Town.-Dick