I'm not sure it's going to make much of a difference inside or outside of your PC case. You just need some metal to propagate the radio waves. https://www.newegg.com/Product/Product.aspx?Item=9SIABP54H31369&ignorebbr=1&nm_mc=KNC-GoogleMKP-PC&cm_mmc=KNC-GoogleMKP-PC-_-pla-_-Network+-+Network+Antennas-_-9SIABP54H31369&gclid=Cj0KCQiAoJrfBRC0ARIsANqkS_4IM0R13wwDc7J_XohcpCEOlRavQLRwlxORRj2GlE-JcYGh5frKfIYaAszZEALw_wcB&gclsrc=aw.ds
Edit: apparently this one is well supported also, and looks like it includes the antennas