I think a trolley is an excellent idea. I have one for shopping, town is approx. half a mile away, and I use it on Saturdays, not for a full shop but for meat/fruit/veg which can get heavy. Useful for taking brolly and waterproofs in case they're needed. I put a small cool bag in it for meat and deli items.
Mine was £14.99 from a local luggage shop, and I've seen them on markets. My advice is get one with a comfortable handle and decent wheels. How much you spend is up to you, but bear in mind it will get bumped up and down kerbs.