Broken Powerblock making my progression confusing

I have an older set of Powerblock Elite USA 90 that I bought secondhand ages ago. Recently I noticed that one of the weights (which I hadn't used in ages broke). It's one of the black adder dumbbells. I'm new-ish to strength training, but I've been working out diligently with Fitness Blender and there are now a lot of moves I can progress to the weights offered by the black set (basically 15 lb, 17.5 lb, 20 lb). Photo provided for reference. But with one of them broken, that means I need to skip ahead to the weight adder weights, which starts at 25 lb per hand. I don't think it's such a good idea to jump up to 25 pounds and I wouldn't be ready to do it yet for a lot of moves. Is there a way to repair this? Or should I do something else like just buy one standalone 15 lb dumbbell?

Here's the progression by color: https://powerblock.com/products/elite-usa-90-adjustable-dumbbells?variant=43064462213311