Even things like cardboard boxes and toilet roll tubes (I recommend to be partly filled with treats and tied with piece of string from the top of the cage) can be used or paper bags.
You can also make an game of hiding food scatter feeding is really good for them. That is putting their food around the cage rather than in an bowl this also stops one rat hogging all the food. Treat balls can also be bought at easter I buy plastic eggs and put treats in them. Every now and again I hard boil an egg and watch them have loads of fun getting the shell off so they can eat the inside.
Good sites to get toys from
http://www.petsathome.com (Not everything is available in store that is online so I recommend to order online and pick up in store. I quite liked the pet parcle but would not get it all the time.)
One of the main things I advise people is to remove is shelves from cages when possible. Rats often wee on them and they can get smelly very quickly. If you don’t want to remove them or can’t as least take the ramp or ladder out. It’s better to make the rats climb more keeps the strength up in the legs.
Wilko’s do some perches, ladders and toys that are listed for birds and some great value treats. The range do quite a lot of bird toys.
I recommend getting the following and using as an perch from Pets at Home
An great perch to help keep nails short can be got from various places Rat Rations sell it.
other recommended perches are from zooplus
It’s not really an toys but I recommend getting an Savic Sputnik you need to get an XL one. Rat rations allow you to pick your own colour here
They can also be got from Pets at Home and various online stores.
Pound shops sell a lot of things you can use but sometimes you would not thing it straight away. I often go down the kitchen and home ware section and garden. Getting things like the over the radiator driers that can be used as perches. Plastic storage boxes and hanging flower baskets that can be used as beds. I have a whole load of Halloween things like the buckets that are used to collect treats make great beds.