This is a tough thread to answer because you can suggest xyz and a second later a dozen people are screaming xyz doesn't have to be expensive, but I will go out on a limb:
Camping supplies. You can camp cheaply, but most people who are not hardcore will want some kind of starter store-bought tent, sleeping bags, sleeping pads, packs, stove, etc., and that can add up. Then, over time, camping vacations save you money.
Maybe asking for cash is out but if there is a particular stock you are really interested in, you could sell that? They might be amused if you explain to them how interested you are in the company and its financials. If they want
some crap something tangible, they could buy one of the shares through
www.oneshare.com/ which will get them a nice framed certificate they can gift wrap and then the balance through your brokerage.
You could also ask for a rain check, letting them know you want to put off big purchases for now in the interests of furnishing your home when you get it. But I imagine you have already thought of that.