Welcome to Sd
what is your budget?
how long a trip do you want him to go on?
what country or remain in this country?
how experienced is he?
does he like/have trophies?
+1
Martin's questions will help scope out what sort of stalking trip is going to be most appropriate for your husband. Regardless, he's a lucky chap!
If you're thinking of staying in the UK then, as other posts have said, stalking for a day in Scotland is pretty much a classic. A trip out after red deer on the Hill, ideally where they still use ponies to extract the deer, is on most UK deer stalkers bucket lists! If your husband hasn't done that before then I'm sure he'd be delighted. If you don't want to head right up North then Colin (solway stalker) on here is in Dumfries & Galloway, so not quite such a long haul - I've done the drive from Bury St Edmunds to D&G before and it's easily manageable. There should be lots of choices depending upon budget, how far you want to drive and how long you fancy staying away.
If your husband has already been stalking in Scotland then an alternative might be heading down to the West Country, where red, roe and sika could be on the menu.
Being in Ipswich I'm guessing that a trip out for muntjac and Chinese Water Deer may not be that much out of the ordinary, otherwise they are popular quarry for those who don't normally have access to them.
Another alternative might be a trip out on wild boar? There's quite a choice available in the Classifieds section. Feral goat could be another alternative?
If your husband has already shot all six deer species, as well as wild boar and feral goat, and has a wall full of fantastic trophies, then what about something like a course on butchery, smoking and curing?
Once you have decided on the details of budget, quarry, distance, etc then I am sure people on here will be happy to help.