Have had the same experience before.
If you can find out something about their interests, then a gift/vouchur is good.
A good restaurant near their locality, that will reasonably cover the cost of a starter/main course for two and a maybe a bottle of wine.
If they play golf - a round of golf at a good golf course.
ditto, horseracing, LoI, GAA (season tickets, framed jerseys signed by players etc)
Tickets to an event, theatre, concert etc.
The gesture of a good gift, regardless of price, will outweigh any cash gift for years to come and may be cheaper than a flat cash amount.