There are a lot of things that one can do if one doesn't have (or want) a therapist.
You can just wing it and survive: after all you've gone this many years without help, so you can probably keep going without it. Conversely, you can turn to other disciplines to see if you can learn from them and take skills from them to help improve things in your head.
Multiples may find support groups for specific issues they are confronting, such as substance abuse, co-dependency, borderline personality disorder, bisexuality, polyamory, transsexual issues, etc. except that multiples can end up hogging up such venues with their own issues. It's probably best to remain sensitive to the needs of other people when you are there.
There are self-help and self-help books, such as workbooks for people who have survived abuse situations e.g. The Courage to Heal (book, workbook). There are workbooks specifically for multiples, such as Amongst Ourselves (Tracy Alderman & Karen Marshall), and there's The Crissing Link: United Front — Positive, proactive and collaborative self-help for people with multiple personalities by The Crisses (Rev. Criss Ittermann), owner of this site and the free United Front Boot Camp blog article listing on the same site. And if you're not decidedly in need of self-therapy, but only self-improvement, nearly any self-improvement book of any reputation can be applied.
There are spiritual disciplines which have a great deal to offer for multiples, and shamanism and voudoun are of particular note. Some spiritual practices have more-or-less reputation in being supportive of possession experiences, internal landscape/external nonordinary landscape, self-hypnotism or meditation, ecstatic discharge of pent up feelings, etc. Be sure you have a supportive environment and that you're not hogging up the limelight, just like any other public/group support structure, you want to make sure you listen at least as much as you talk. If you find yourselves becoming a drama magnet, you might want to reassess why you are attending the group. Such groups are not group therapy sessions, and everyone is there to get something from it.
On that note: it might be possible to be in group therapy without having an individual therapist. If so, it's probably best to seek out a group therapy specifically for multiples. You might also seek out a support (as opposed to therapy) group.
With the continuing maturation of the coaching industry, it may be possible for a multiple system to receive guidance and motivation from a (life, motivation, wellness, business, career....) coach. A coach who understands multiples would be best, but they're probably few & far between (for one, see The Crisses' coaching website). If the system agrees to be coached as a whole it may be possible to work on external life goals with a coach who has no clue that you are multiple.
There are spiritual disciplines and energy work that has benefit for many people, such as shamanism, Reiki, and so on.