As I see it, you need to develop a business strategy for the season by taking advantage of your the resources you already have. Obtaining additional funds will help you to alleviate your financial constraints, but from what you have told this doesn't appear to be the most attainable solution to your problem.
For developing a business strategy with the objective of keeping your shop open during the winter, there are some aspects you could take into consideration:
1) As the demand is low during winter, you will have excess capacity, which is actually the source of your problem. You may think of offering very aggressive promotions for both existing and new customers, with very low prices on the services and goods. Your primary goal is to cover the operating costs, not obtaining a profit.
2) You may provide free services to attract customers, such as workshops on bike maintenance. You may also consider exploring strategic alliances for these activities. For example, you could organize activities sponsored by one of your providers, in order to educate your customers on the advantage of his/her products and on how to use them properly.
4) If you have enough space, you could setup an indoor training business. This could also be achieved through strategic alliances, for example with bike instructors.
5) You may sell your goods with a minimum margin above the replacement cost, specially the one with low turnover rate.
6) After 6 months, you probably already have a customer base. Try to think what value proposition you could offer to them, based on your knowledge of their needs and the resources you already have (the shop, the know how, your stock).
There are a number of techniques to develop ideas about business models, such as the Business Canvas and the Lean Canvas, which provide you with a structured approach to think about your value propositions, your customers, your resources and other critical aspects of the business.
Regarding the additional funding, you may try Crowdlending, not to cover your entire expenses through the winter, but to alleviate your financial stress. In order to get better chances with Crowdlending, I think it will help you to have an appealing business concept with a reasonable ROI, as opposed to simply requesting money for working capital.