eBay is going to be your best bet. There are many 1:6 swords, shields, daggers and such on there, from low to very high prices, depending on what you're looking for. There are also some companies that make miniature collector sets (some in 1:6) with swords and other items in them. I'm really not that familiar with what is out there but I have seen some of the ones created by Master Replicas several years ago for "The Chronicles of Narnia" movie and they were very nice. When searching for items on eBay, it all comes down to the search terms. You can try "1:6 sword" (or dagger, shield, etc.) and possibly find what you're looking for but also try terms like "miniature sword" as well. Look closely at the item description and if the item's dimensions are given, it should give you a good idea if it's suitable for 1:6 use. Another source is letter openers. Try searching for "sword letter opener" and again check the dimensions to see if it's suitable. If you don't mind a little customizing such as cutting, filing and painting, also look at keychains and necklaces and use the same strategy and check the dimensions. If the dimensions aren't given, then feel free to contact the seller. Here's a link to an eBay listing (not mine) for a lot of three of the Narnia sets that I mentioned to give you an idea of what I'm talking about as far as the collector sets are concerned:
Chronicles of Narnia 1/6th Scale Master Replicas Susan Lucy and Peter Gifts | eBay
You might also like to take a look at this site. It turned up in a Google search and they have miniature weapons and letter openers. When you click on an item and go to it's page, there is a tab that you can click for the dimensions. Here is the miniatures section of the site:
https://www.medievalcollectibles.com/c-337-miniatures.aspx