There are an overwhelming number of options for choosing a domain as your branded URL for shortening.
The important things to remember are:
1) Extensions such as .link, .sale, .brand, .click are fun and they work as well as, for example, .com or .net. So, don’t afraid to use funny and little-known extensions.
2) Short links are better nowadays than long links. However, don’t forget about branded links, it is more important than short links.
3) Please, be focused on how you can represent a strong brand. For instance, you can remain the most significant vowels of your brand name in order to save some space.
Our advice for you is to choose the same name as your main website, but with different TLD. For instance, instead of "phone.com" you may choose "phone.link" or "phone.click".
As well, you can use a subdomain of your main domain, such as "buy.mybrand.com" or "choose.mybrand.com." We advise it, but it is easy to service and completely free for you. More information about using of sub-domains as branded short URLs you can find here.