Pentax 50mm F1.7 is a very good choice partnering with the Pentax K1000 having the wider aperture than the standard F2.  This example is the 'A' version which can be also used with digital K-mount Pentax cameras.  Near mint condition.  Can also be used with adapter to Sony E-mount. You can buy this lens for your K-mount or choose the option of adding a K&F precision PK-E adapter which enables this lens to be mounted on Sony E-mount, focus peaking cameras.  Both lens caps.

Pentax - A 50mm F1.7 K mount S#1580336