What large bore griego mouthpiece would be similar to a wick 5al?

I think Griego Artist (Alessi) 5D, 5E

The Griego artist numbering is based on the Greg Black numbering, so the 7 in the artist series would be the closest. For the regular mouthpieces it would be 5.

Using Doug Elliott's comparison charts as reference — and recalling how the (old) Greg Black numbering translates, which Doug used — I think the artist F cup would end up being the closest to a Wick 5AL, but a bit shallower.

Recently Griego came out with an artist 6 series with an inside diameter of 1.014". In your case I'd give both the 7F and 6F a try. One may "feel" a bit narrower, the other a bit wider, but both shallower than, a 5AL. Ymmv.

In the classic line, the 4.5 might be the closest based on Griego's specs.

Sorry guys I disagree with some comment. I play a Griego Alessi 5 and can assure you it feels slightly smaller than a Bach 4G, a Greg Black New York 5 and a Doug Elliott 102 rim. This is because not all makers measure the inner diameter the same way. In my experience Griego Alessi 5 feels like 25.75 mm diameter, comparing with other brands. The Denis Wick 5AL has a diameter of 25.73mm that's why I gave this advice. I also played it several years ago on a Griego Alessi 7 series, and it feels pretty much like a 6 1/2 Bach.

I don't agree with recommending cup F, because it's deeper cup of the series and probably only suitable if you play second trombone in a big symphony orchestra, I wouldn't call it an all-around cup. If you really want a deep cup go for a D or maximum an E.