For companionway hatch
I had some stainless grates fabricated in Ecuador
similar to those on James Baldwin's site. Quotes in US were $800+. Cost in Ecuador
was $120 and had them the next day...but that's another discussion.
For my deck hatch
I made up a prototype of stainless bars and L-brackets. A top piece and bottom piece "sandwich" together at right angles and are fastened with a padlock. These only work with the hatch open so really only for anchorage. But...I like that I didn't have to modify the hatch or drill any holes.
I did make one out of 3/4" aluminum
but was able to saw through with a hacksaw in less than 30 seconds. The current
version is 1/2" stainless that costs/weighs more but seems to be the better choice. L-brackets are 3/16". Hopefully the pics make it clear.