Except antique shops there is a lot of museums with arms and armour to see. In Warsaw only one

it is Muzeum Wojska Polskiego (Museum of Polish Army), in my city 4
Muzeum Narodowe (National Museum) where I'm working and where you can find the biggest exhibition of arms and armour in Poland (over 1600 objects)
Wawel Castle with beautiful, partially Royal collection of arms
Cartoryski Museum with arms, armours, paintings, etchings and the famous Leonardo da Vinci's "The Lady with an Ermine" painting
You can also see Muzeum Historyczne Miasta Krakowa (Historical Museum) and Muzeum Archeologiczne (Archeological Museum) in both there are some arms on exhibitions.
I think you should consider the plan of the trip and come to Cracovia for few days more, one week is to short!

(and I don't mention beautiful monuments - bah, you'll need around one month

)
If you'll have any questions please mail to me, I'll gladly help you. If you'll need a guide on National Museum collection contact me!, I'm working there in Military Department. If you'll be in Cracovia between Monday and Friday, maybe I'll be able to show you magazines where you can find (among others 10,000 miltary objects) around 100 yataghans, nothing special I think, we still miss some important pieces, but there are some worth of seeing

Regards!