Lol. EEVblog is turning into donation central. You could just save up... perhaps? Even a CHEAP DMM is only a matter of £20. HOWEVER... if you want to review a multimeter, you have a VERY high chance of getting to keep it, once the review is done. You don't need to plead poverty when approaching the company or supplier -
think like a pauper, you'll come across and live like one; you simply approach them, professionally and confidently, ask if they'd like for you to review their product on your YouTube channel, and offer links and mentions of their site, in return. 9/10 companies will allow you to keep low value items - but that SHOULD NOT be the motivating factor for approaching them - you need to want to review it, BUT, it will provide a mutually beneficial solution to a problem I do not even see existing, as advertising costs them WAY more than the cost of sending you a meter to review
Trust me, this is coming from someone who's done this for years, and they appreciate a good review, and are more than willing to allow you the small token of keeping something in exchange for an honest review. I've done reviews of many things, from coffee grinders to a multimeter, myself (Oh, and a few times, MUCH more expensive items)
All the best.