Cindy, there are some great recommendations here, but there's another approach that's missing. I'm not shy, but I am an INTJ, so I do know how you feel. My batteries drain in socializing and recharge in solitude, so I've had to learn to manage this for my own good - to the point of being able to deliver 300+ speaking engagements and lead a large professional association for several years. Since you are interacting with others (facilitation, consultation) at the core of your business, it makes sense that you probably don't have much energy left for sales and marketing.
First thing is, if you're in a hurry for whatever reason (e.g., money running low), you will need to either (a) force yourself out of your comfort zone or (b) find an extroverted sales partner like you mention. You can't let your introversion or shyness lead your business to stagnation or failure. Steve Wozniak (very shy, probably on the autism scale) had Steve Jobs, and there are many similar business examples.
However, if you have time on your side, I think the following approach may be ideal.
It's best summed up by Seth Godin: "Become famous to your family." Your "family" is simply the market you seek to serve in its most narrow sense, with the actual decision-makers being the family members. Your goal is to be discovered by them, not necessarily push yourself on them. Thus, it's a passive marketing approach, which is very ideal for introverts. It takes time, however, because you need to build an online presence that attracts your target audience to you. This could be a blog, Facebook or LinkedIn group, YouTube channel, Udemy course, Kindle book, or any combination of these. Through this/these media, generously share your expertise. It's not about selling; it's about "being famous to your family." When your target audience sees that YOU are the go-to person in your area of expertise and they have a need for your expertise, they will naturally reach out to you. Again, this does take time to build; however, all of it can be done from the glorious solitude of your computer!
Another suggestion I didn't see mentioned above is building a cross-referral network. These can be similar experts with whom you can share work overload or good prospects who aren't an ideal fit -- or they can be complementary experts; i.e., consultants or service-providers who serve your same market. An example of this in my field is book editors and book designers. And to the former, a lot of publishing consultants and project managers swap and share prospects for the right fit. As with what I mentioned before, in this digital era, all of these people can be found online.
Lastly, for the overall challenge of living as an introvert in an extrovert's world, check out Susan Cain's book Quiet and her accompanying TED Talk, "The Power of Introverts" (over 13 million views). I guarantee you that you'll feel better about yourself, come to learn that shyness is not the "problem" that society often labels it to be, and recognize that many of the greatest thinkers, inventors, and innovators in history were introverts. You can succeed on your path as well!