I have had the silver pen for about 3 years now, and have only replaced the cartridge 1 time. The black pen with stylus was purchased about 3 weeks ago when I bought a new smartphone. the stylus is quite handy and has definitely helped me to preserve my screen. Also when I need to make a note quickly on my phone I can use the pen without needing to clean off my hands first. The clip on the silver pen, unfortunately did not come with it. I robbed the clip off of a cheaper mechanical pencil and bent it to fit. There are space pen bullet clips made for theirbpens, but price and availability convinced me to find my own way.
Most of the Space Pens can be had for around $20 but between Amazon, Ebay, and office stores, it's likely you'd be able to find one for considerably less.
Fisher Bullet Space Pen
Length: 5.3" open, 3.8" closed
Composition: All Brass, chrome finish
Refillable?: Yes, Fisher PR4
Writing Conditions: -30°F - 250°F; Any angle; through oil, grease, rain, underwater; zero Gravity
Warranty?: Unconditional Guarantee
Available Variations: Chrome, Matte Black, Desert Tan, Brushed Chrome, Raw Brass, Lacquered Brass, Blueberry, Hot Pink, Lime Green, Red, Pink, Copper, Bronze, Black/chrome, w/stylus, w/o stylus, Rainbow, American Flag, space shuttle, and more.