Shaun, Yuasa makes excellent trickle chargers; I've been using them for more than 20 years (starting with the model prior to the one in my link - have 5 of the linked ones as well) - never had one stop working or exhibit any sort of problem.
It is only 1amp, however, not 3 like you mentioned you might want.
Here it is in this Amazon link.
https://www.amazon.com/gp/product/B07K5XF1VC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1