Sometimes lost parts to things can be remade with Sculpey or similar oven-bake clays.
You will need some Sculpey, an oven, something to use to shape the Sculpey, and something to use as a work surface, as the colourants in Sculpey can stain some surfaces before the clay is baked. Optional is aluminium foil, to make a basic inner shape with, so that you don't use too much Sculpey.
I use the back of an old plate as my work surface, as it is non-porous, easy to clean, and the Sculpey doesn't stick to it too much. My modeling tools are toothpicks, an old knife and a manicure kit. This last seems strange, but is very useful, as the tools have different shapes, and are a good size.
Also, my heartfelt apologies for the terrible quality of the photos. I originally made this tutorial for a MLP fan site back when everyone had dialup o.O
Before you start, look at pictures of the item you want to replicate to get a feel for how it was sized and shaped. It's a great help if you have a hard copy picture to refer to as you create your replacement.
First, make a base shape out of aluminium foil, this is so you use less Sculpey. For the 'Lipstick' I am recreating, the base shape should be about 1.5 to 2 cm high, 1.5 cm wide and cylindrical.
Using a base form will mean less clay is used, which translates to less baking time.
Next, cover this with a thin layer of Sculpey. This layer should be about 2mm thick. The colour I used was Lavender, which was the closest shade I could get without resorting to mixing clays. On top of this preliminary layer, you will need to apply four evenly sized "petals" which give the lipstick tube it's segmented look. These also give the tube an hourglass shape.
Make sure the grooves between these "petals" are fairly well defined. Use a sharp tool, and scrape to make the grooves bigger.
On top of the tube are two concentric cylinders, fairly flat, the top one with a hole in which some felt is later put (to be the 'lipstick"). The top one is about five millimetres across, the bottom one is about sixteen millimetres across. It's a huge help if you have the original top to the lipstick to make sure these are the right size. (If not, make and bake this first.) Make a ball out of Sculpey, and flatten and shape into a flat cylinder, and stick to the top of the tube. Use a flat tool to help shape it once you've stuck it on. Do the same for the smaller cylinder.
The front and back of the tube each have a heart, which covers one "petal" and overlaps the side "petals" by one or two millimetres. This heart has a groove running around it's edge. use a sharp tool or toothpick to make this groove, it's about one millimetre from the edge of the heart.
Smooth out your work, eliminating any rough edges. Bake, as per instructions on the packet. Glue a small, folded over piece of red felt into the hole you left. And now you have a nice new lipstick tube for your pony.