I've done this initiative www.met.police.uk/police-forces/metropolitan-police/areas/campaigns/2018/met-christmas-appeal/ for a few years but usually get girls to buy for. They've been easy.
This year I've got to buy for an 8-year-old boy and I'm not sure what to get so all ideas would be very welcome. The budget is around £20-30 I think and I usually try to keep presents on the small side since the children may be in temporary accommodation with not much space for storage.