Try your local riding school, they will almost certainly have capable and experienced clients looking to loan/share/buy who they can put you in touch with.
Our YO could probably could about a dozen people at any one time. Good loan horses are difficult to find but it is often a popular choice for people looking to make the move from a riding school before they buy thier own.
Most people, understandably, want to loan their horses but keep them on the yard. Its the only way you can be assured all is ok.
Having just loaned one and had to take it back due to condition and lack of attention we're now being held to ransom over the passport. They are demanding past 6 months livery as they say 'wouldn't have taken him on if known he could be removed'. They don't have a leg to stand on and the horse is safe and hopefully on the mend. These people 'claim' to have another loan horse arriving very soon. I'm just sad for the horse, and hoping the owners keep an eye on it. If its true.
But against that we have 3 others that are out on loan and I couldn't ask for better homes! I don't interfere, they send photos and updates and I know that should I feel the need to check they will answer the phone and put my mind at rest.
I have horses that I would cheerfully share, if someone wanted to ride or compete they would be welcome...i'll even transport them! I like the horses kept stimulated, and love to see them giving the riders some fun. I also have one to loan out but i'm reluctant to advertise. Mine have all gone by word of mouth, so my advice is to tell as many people as you can that you are looking and what you hope to do with the horse!
I will be looking for a loaner for my nf gelding next year when he as been proffessionally started but i will want him kept at home. There will be no charges just someone experienced in youngsters but this type of loaner is harder to find not all people like babies.