There are many possible options for the table surface including:
Tempered Safety Glass
Tempered glass can be purchased from your local glass supplier.
They will also shape the corners if you request it.
It's a relatively expensive solution, but you can customise the size to your exact needs.
We'd recommend a small overlap of around 1-2cm.
Square fire pits - 63cm square glass.
Rectangular fire pits - 93cm x 63cm glass.
Made from tempered glass or stainless steel, these are widely available at 60cm square and 60cm x 90xm rectangular sizes from around £40 delivered.
Glass splashbacks tend to have painted backs which are not usually very scratch resistant, so some care must be taken when placing them on your firepit. They are available in various colours - but usually black, grey or white.
Stainless steel splashbacks can also be purchased, but be careful with these as edges are usually sharp so they are not ideal.
(Stainless steel will also develop rust spots if left outside.)
Acrylic / Perspex
Slightly cheaper than glass (and safer), acrylic or perspex sheet can be bought online and cut to any size.
These are available in almost any colour.
Prices vary depending on the colour but can be purchased from around £30 for a 60cm square piece.
Wood will need to be treated to protect it from the wet, but is perfect if you wish to match your fire pit's look to wooden furniture.
You can often find second hand square table tops you can use to cover a 60cm square firepit but do bear in mind they may not last long outdoors!
Corian is an expensive but robust table surface and is available in various finishes.
Off cuts of corian can be obtained relatively cheaply compared to new.
Large Floor Tiles
Floor tiles are available in sizes over 60cm and can be used as a tabletop.
These are probably the cheapest solution as odd ones can be picked up on Facebook marketplace and ebay very cheaply.
Slate / Stone
A natural slate or stone slab can work really well. Just be aware that these can be quite heavy so be careful when lifting them.
Our firepits are very strong so won't have any issues supporting lift-able surfaces.
Glass will happily sit atop our firepits, but you may wish to add some felt or rubber sticky pads to the corners to prevent scratching.