Nick here from Shopify. Great question and good research so far!
Locksmith would be my favourite app in the Shopify App Store for this type of feature also, but there are some other options you could look into and consider too. You can take a look at them below:
I think an app is definitely the best way to go for you on this, but you could also consider having something custom made for your store also by a Shopify Expert. It would be a higher upfront cost, but it wouldn’t be a monthly cost then like the apps would be. You can see the Shopify Expert directory here if this was an avenue you wanted to consider.