>> source: https://www.nigella.com/ask/substitute-for-suet

If you can't find suet then we have found that grated @vegetable shortening{1%stick} (such as Trex, Crisco or Copha) is a good substitute. To grate the shortening firstly freeze a stick or block of it until firm but not solid (this usually takes about ~{30%minutes}).

Grate the shortening on the coarse side of a #box grater{} into a #cold bowl or onto a cold plate{}, returning the fat to the freezer if it becomes too soft.

Before using the grated shortening chill it for another 10 to ~{15%minutes} in the freezer.