Maybe he'd like a big hunk of meat or fish?
Honestly LOs don't need teeth to eat, they can manage just about anything (not whole nuts), their gums are very very hard.
Banana isn't slippery if you don't slice it, just give it whole (or snap in half if you don't want to waste the whole thing). Crescent shapes are easier to pick up so if you slice the avocado into wedges you naturally get a crescent shape when the seed was removed, the 'bend' give a grip point even though the slice itself is somewhat slippery. The thing with slippery or trickier food to pick up also is that it is fantastic practice for their fine motor skills.
As he takes toast I would expand on the breads you offer to give his tastes a variation on something he already quite likes. Pitta bread, chapatti, flat bread, garlic bread, bread sticks... they all offer different textures and flavours.
What is he like with veg? Steamed carrot batons, green beans, asparagus, sweet pepper stick; baked sweet potato wedges or potato chips (fries) baked pear or apple wedges; roast potatoes, turnips, carrots, beets.
Omelet is great for breakfast, or an oven cooked fritata with cheese and veg in. Bean burgers or falafel are easy to pick up and very healthy.
My LO ate with a pre-loaded fork from 6 months (I started with a plastic fork at that age, and I held the back end of it not to feed him but to avoid any accidental stabbing, we had moved on to kid sized cutlery by 10 months so he had a 'real' fork) which is easier to eat with than a spoon. Spoons actually take rather a lot of finesse to use (and a further development to the wrist action which LOs don't yet have), forks don't drop their load when tilted in the 'wrong' direction so are easier and really help with the slippery foods too.