Is there any clever way to make a slightly to <ahem> generous high-heeled shoe a bit smaller?

[PacificDogwood]

Wonderful ebay bargain - Timberland Stratham Heights pumps and they are fab.
But - about 1/2 a size to big. Just fine with (woolly) tights, but will occasionally slip off my heel if worn with bare feet.

So, any ideas, fashion ladies, or should I just learn my lesson and not buy footwear on ebay without being able to try stuff on ?

TIA

Heel grippers you can get them in boots

An insole will help too