I want to bye remington hc 820 - Remington Precision HC-820 Hair Trimmer

You will find a replacement charger for model HC-600 at shaveroutlet.com. See link below

http://shaveroutlet.com/shaver-replacement-parts/cords-chargers-and-stands/remington/remington-hc-600-charging-cord.html

The Remington Model HC-912A has adjustable blade with a lever on the side, you can use the Wahl attachment comb. You can this this at
Manny's Sharpening

You will find at shaveroutlet.com. See link below

http://shaveroutlet.com/shaver-replacement-parts/remington-hc-600-charging-cord.html

You will find a charger form Remington HC-600 at shaveroutlet.com. See link below

http://shaveroutlet.com/shaver-replacement-parts/remington-hc-600-charging-cord.html

Ask your friends for spare.If not buying a new brand is the solution

You will find at shaveroutlet.com. See link below

http://shaveroutlet.com/shaver-replacement-parts/remington-hc-600-charging-cord.html

You can order this item from shaveroutlet.com. See link below

http://shaveroutlet.com/shaver-replacement-parts/remington-hc-600-charging-cord.html

You will find the comb set for model HC-8017 at shaveroutlet.com. See link below

http://shaveroutlet.com/remington-replacement-guide-combs-for-hc-8017-hc-920-hc-921.html

You will find the offered at shaveroutlet.com. See link below

http://shaveroutlet.com/remington-replacement-guide-combs-for-hc-8017-hc-920-hc-921.html

The part that you require is not available for budget models like the HC-8017. You will need to purchase a new clipper or find an old one (ebay?) that you can buy cheaply for parts.
If you decide to replace your HC-8017 clipper, you will find them for sale at shaveroutlet.com