I don't know whether the AL4 casing will fit the older engine design. You could check the part numbers to compare.
My suggestion, if no 2nd hand engine covers can be sourced from a scrap yard, swap column, etc:
Step 1: go to your local spares shop and ask them to compare the casing gaskets, to determine whether the screw holes line up with each other and they are the same shape gasket. This is the least expensive test. If they don't line up or the shape is different, then it's pointless to continue looking for an AL4 casing. If they line up, then step 2.
Step 2: take your damaged cover along to your spares dealer, to compare the old cover dimensions to that of the new cover plus the prices of each. Not all spares departments would have this cover in stock. Few spares departments would order a cover, just to sit on it, if you don't intend buy it.
Step 3: decide what your budget is, then decide on the way forward
Refurbishment may be the better option in the end.