You're best off prefixing (to get a .com) or going with an alternative TLD. Don't get a .net or .org though, because they just don't have the same appeal. Maybe try one of the new TLD's (.academy, .guru, .sexy, etc)? Also, don't worry about the effect your domain may have on SEO. Focus on solid content marketing and the SEO will come - use paid traffic and a good autoresponder series if you have to spend money on marketing.