Do you want to share and limit yourself to say 2 slices, or have a whole small pizza to prevent yourself from eating more than planned?
Looks like the best option for slices is the small thin crust florentine at 117 cal per slice, so about 6 syns, and 6 slices so about 36 syns in total!
The 'personal pizzas' seem to be 4 slices, and using 1syn =20 cal
-veggie supreme (Delight mozarella) is 524 cal so 26 syns
-texas BBq (delight mozarella) is 518 so also 26 syns
-cheese and tomato (delight mozarella) is 505 cal so 25.5 sys
Just out of curiousity looked at the worst ones, the large dominator perperoni passion has 351 cal per slice and 10 slices so 176 syns in total! Though not sure who could eat a whole one lol Whatever you do don't pick any of the sizzler ones. The meaty ones are really high.