I have found a great way to save a heap of money on dish wands that dispense dish washing liquid from the handle while washing.

Its an easy process to replace the sponge / scourer with a fresh one, without having to replace the plastic part too often.

To buy replacement heads/sponges (in Australia at least) cost about $1.50 each. Replacing them yourself works out to about $0.30 each

You will need:

A dish brush / wand with a soap reservoir in the handle (prices for these type of products varies)
The old and worn out dish brush / wand head
A new sponge with scourer on one side - 3 packs of cheap brand sponges/scourers are about $2
Glue - I have found Tarzan Grip General Purpose Glue works very well, and is about $5
A pocket knife or similar
Marker pen
Scissors
Optional - a 1kg weight

Step 1: Remove the Old Sponge From the Plastic Base

Here is an old and worn out dish brush/wand sponge, and a cheap new sponge/scourer that we will be using to replace the old one.

Firstly, pull the old sponge off the plastic base, then carefully use a pocket knife or similar to scrape away the excess foam and glue. IMPORTANT: Always scrape the knife away from your hand holding the plastic. Try and rest it on a firm surface, but don't press too hard or the plastic will crack.

Don't be too fussy, just remove the bulk of it, and any build up of glue.

Step 2: Mark Where to Cut the Sponge

The first image shows the cleaned up plastic head/base.

Mark the sponge so it is slightly wider than the base. Depending on the size of the sponges and the plastic head/base, you should be able to mark the sponge in thirds (ie. you can get 3 replacements from one sponge, 9 in total for a 3 pack of sponges).

Cut the sponge along the line you marked.

Step 3: Glue the Sponge to the Plastic Base

Place two strips of glue along the plastic base, as shown in the first picture.

Don't place glue too close to the hole in the middle of the plastic base (where the soap comes out).

Position the base centrally on the sponge. Gently push on the base to make sure the glue can adhere and soak in to the foam a little.

Step 4: Place a Weight on the Plastic Base, or Just Wait

I personally put a weight on the sponge for a few hours to make sure the glue joins them together well, but I don't know if it's necessary.

Once the glue has set (10-12 hours), I leave it for another few days so that the smell of the glue dissipates. If you don't, it can make the dishes smell a bit unpleasant.

And that's it!! You've now got a cheap replacement that works just as well as the original.

A few other tips:

The plastic base will eventually crack/perish, but I havent kept track of how many replacements I get out of one plastic head/base. Maybe 3-5? I think it depends on how rough I am with removing the glue, and the amount of heat and work Ive done with the dish wand
I prefer not to use concentrated dish washing liquid in the dish wand. The cheap / standard stuff works just as well and flows better without having to water it down (see next point)
If the head isn't getting soapy enough, add a little water to the liquid in the handle. Don't make the hole bigger
Bonus Tip: Most of these heads have a plastic edge at the top (check the picture), which is designed to scrape off the excess and caked up waste on your dishes... something that took me awhile to realise...

Hope that helps, and saves you some $$$ :)