The grey Tigers were rather specific and unusual. Most Tiger kits don't build them.
The batch of 9 Tigers sent to Leningrad with the 502nd, are addressed by only one recent kit:
Dragon's #6600.
That same unit then got another few grey Tigers. They were promptly whitewashed, but they're counted in my total. A future kit from Dragon will build one of them.
The last remaining grey Tigers are the nine sent to Rostov. They had a unique turret bin and they didn't have the S-mine system (which affects the tool layout on the top deck).
Only one kit builds those Tigers:
Rye Field's #5003. These ones apparently spent some time in their grey paint before getting whitewashed. Rye Field don't provide decals for this period, though.
You asked about numbers. We don't have enough photos of these Tigers to be sure of the exact numbering, but we can see some of them.
The first ones at Leningrad were apparently numbered :
100 101 102
111 112 113
121 122 123
When the extra ones came, they and the surivors were all renumbered a couple of times :
1 2 3 4 5
And the ones at Rostov seem to be:
200 201 202
211 212 213
221 222 223
David