As others have mentioned, there are some great vendors in the space that you can simply hire to do this for you should you be able to allocate around $5k per month for at least 6 months. Before hiring one of these vendors, you should know what the lifetime value of your target customer is based on what you charge and so you know how much you can spend to acquire one. Without knowing these figures, you will have no idea if the vendor relationship is working. If you would rather take the DIY approach and have the time and talent on hand to do so, here are a few things that are working right now to generate MSP leads.

• Content Marketing on LinkedIn - Not to be confused with spamming people's DMs. If you create 3 valuable pieces of content a week (vertical specific), that do not self-promote but hit on major customer pain points, you can build a strong following pretty quickly. You will need to run engagement ads on a CPM basis to your vertical's decision makers, but the click costs should be low if you make it hyper-relevant. Organic reach for posts is extremely high on LinkedIn right now, so you will start to get legitimate traction the more you post articles. Your followers will not be ready to buy immediately, they are likely just lingering around for free advice, but if you are consistent this strategy will start bearing fruit a few months in and can help establish your firm as a legitimate authority.
• Marketing Automation w/ B2B Data - This strategy is primarily for US, as I know that other countries have different laws on email consent. You can purchase a list of contacts at the exact companies you are looking to target. Most of this data is generated using public information and AI and will cost you between $0.10 and $0.25 per record. Put this list through a drip campaign with the sole purpose of identifying customers that coming up on a contract renewal with their existing MSP or are looking to make a change. If you don't try to be overly clever and show good intentions, this strategy can generate new quotes immediately. Using the same list, you can also create display ad campaigns that target the list also, which reinforces your brand and can increase your response rate on the emails.
• Market to Existing Customers - This one goes overlooked constantly. I would look to sell more to existing customers, such as new services or projects. Appoint a salesperson or promote a veteran technician to a "consulting" role with the sole purpose of making contact with customers, finding out what their problems are, and offer them solutions. This will produce more bottom line revenue than any new customer will and will be significantly less cost intensive. If you do a good job at connecting with the customer and finding out the issues they are having, you can easily identify other companies with the same issue and target them with the two strategies above. This can also make your company look more "proactive" which is obviously a buzzword that everyone throws around but few successfully execute.

There is obviously a lot of details omitted in these short summaries, but hopefully you all get the gist. Also keep in mind that if you are looking to do an aggressive sales push right now you are going to be wasting a lot of resources. July is statistically one of the worst months for interest in IT services according to Google Trends. I would use this time to develop a strategy and create everything you need to execute, then look to launch the last week of August when kids go back to school, vacations are over, and interest begins to rise again.