There is an oriental museum : Museo do Oriente
I have never been there, but assume that oriental weapons will also be on display. You can check their website :
www.museodooriente.pt
At this moment they have an exhibition about India.
A wonderfull hilt of a Kastane is on the poster
Have a nice time there.
Would love to hear/read your findings after the vist.
Best regards,
Willem