We do lots of Montessori inspired activities as he prefers those to his toys! They are good for staying a bit quieter as LO has to focus on the activity, and if it catches their interest then they really do focus on it, sometimes for ages
All you need are a few household items and trays to set things up on
DS loves pouring (beans, lentils, rice, coloured water) from one jug to another - try to use two small jugs of the same size that he can handle easily, and have a cloth handy for him to mop up any spills when using water. You can also introduce a funnel.
He also likes posting items - money into a moneybox, pasta into a cereal box with holes cut into it, ping pong balls into a box, anything you can find!
DS isn't so hot on scooping and transferring, but it's an easy one to set up with a spoon, a small bowl, an egg carton and some beans / marbles etc. You can also try him with tongs or tweezers and pom poms.
He does enjoy colour matching, which we do with coloured paper circles in a bun tin and matching coloured pom poms to sort into each hole. You can use coloured bowls, cups, anything you have. I've seen a few neat ideas using clothes pegs with colours painted or glued on and a matching strip of colours from the DIY store paint mixing charts
Clothes pegs can also be used to peg around a pot, or to peg up cloth pieces on a mini washing line. The other idea I've seen is to paint them and make them into legs for a cardboard horse (or any other animal) which you've made the body and head of..
If you don't mind a bit of mess, you can give him a sink / float bucket - collect objects and see if they will sink or float in a bucket of water. He can also try to fish ping pong balls out of a bucket with a tea strainer or a small net.
You can make up a fishing game with some cardboard or craft foam fish with paperclips on their noses, and a magnet on a string tied to a chopstick.
A brilliant no-mess painting idea is to use a ziplock bag with a few squirts of different paint inside, taped down to the table, so he can use his hands to mix the colours around. You could also add glitter to make it a bit different.
Hopefully that'll get you inspired, and if you google 'montessori activities' you'll find lots more ideas