You can charge your Apple Pencil directly [and very rapidly] from your iPad. The inline adapter, used to charge the Pencil from your Power Adapter, is only intended to for “trickle charging” the Pencil.
The inline charging adapter is not sold by Apple as a replacement item - however, if you contact Apple Support and ask very nicely, they may be able to help. Similarly, should you visit the Genius Bar at your local Apple Store, along with a healthy approach to requesting help, they too might be able to assist.
Alternatively, it is often reported here that is possible to purchase a third-party replica from a popular online retailer or auction site. Being totally passive, the non-OEM part carries little risk of damage or other issues.
Apple Support can be contacted using the Contact Support link at top-right of this page.
I hope this information proves to be helpful to you.