Difficult question. I have the same problem and recently, after an extensive review of alternatives, decided to buy an Epson Perfection V700 for this purpose. My old HP also wasn’t good enough.
I was thinking about a Nikon film scanner, but they are single purpose and are overpriced in this country. The secondhand market also seemed to be poor.
I read a good review of the Epson, which made me decide to go that route (search on Google). It is a nice scanner, and can do 12 slides at a time – this is important, it takes about 4 minutes per slide. Quality seems OK, not as good as I had hoped, but this may be a reflection of the poor lenses that I had at that time and slide deterioration over time. It also has the Digital ICE feature which removes dust and scratches – this really works well.