You may think self-discipline means doing it all on your own.
It doesn't mean that at all. In fact, having a coach, a group, or an accountability partner can help you develop self-discipline. An example would be when you put off housework until you know someone is coming over, and then you race around to get the house all clean before they show up. It's easier to give in when you are only accountable to yourself. When you have people to hold you accountable, you are far more likely to reach your goals.
Using the buddy system to build self-discipline.
An accountability partner is someone you agree to meet with to hold each other accountable for reaching goals and developing your self-discipline. Of your options, this is probably the easiest to set up. Your goals do not have to be the same. The point is to connect regularly, usually once a week, and share with each other how much you have accomplished. The best way to do this is to break up the task into daily chunks and do each one each day so that you are not trying to finish up the project the night before you meet with your accountability partner.
It's easier to schedule a meeting with one person rather than a group of people. Rarely do you pay for this method, as you will pay for most masterminds or coaching services. You also have more flexibility in how you meet with an accountability partner. Some options available are to talk on the phone, use an instant messaging program, meet for lunch at a restaurant, or meet at one of your homes.
It's not always bad to be a part of the crowd.
If you like a more interactive approach, then you may look into joining a group, like a mastermind. The advantage of having a group is additional pressure on you not to let the whole group down. When you run across an obstacle, the group can help you brainstorm ideas. Two heads may be better than one, but sometimes multiple heads are much better than two.
Find a professional to give you the boost you need.
You may find that you have a deeper issue and want some more direct coaching to help you strengthen your self-discipline practice. Maybe you are trying something new and need teaching and connection. One-on-one coaching can be the most expensive option since you are taking up your coaches' time. Group coaching is becoming more available because it allows the coach to help more people. This has the added benefit of having other people that can help you out with specific issues, similar to a mastermind. These usually cost a lot less than one-on-one coaching as well. Which may be more within your budget.