You probably won't "find another block and tackle" advertised anywhere. You just buy the appropriate blocks and
rope and make up your own.
They are old Ronstan blocks (RF 1256 and RF1257). Ronstan have since changed their model numbering.
You probably need one each of their 51200 (1256 replacement) and 51210 (1257 replacement).
You can get them and a suitable length of 5/12 (8mm) double braid
rope from any
marine chandlery.
Can't help with the brackets.