The classic scale for Traveller miniatures is 15mm; and, luckily, in the last decade or so, this scale has enjoyed a renaissance of sorts, and there are A LOT of minis available.
First, there is 15mm.co.uk, which provides both the classic Laserburn range AND very good new miniatures, from starfighter crews through shabby mercenaries to armed cultists and various aliens. Highly recommended!
Second, there is GZG (http://shop.groundzerogames.net/), who provide a ton of 15mm minis, vehicles and terrain, including a proper ATV!
Third, there is Khurasan Miniatures (http://khurasanminiatures.tripod.com/adventure.html), who have several very imaginative sculpts, including "Aslan" in Powered Armour.
Fourth, there is RAFM (http://www.rafm.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=RAF&Category_Code=GRAV), which has some of the old "not"-Traveller minis available for purchase, including (but not limited to) Vargr, Aslan and Droyne.
Fifth, there is Stan Johansen Miniatures (http://www.stanjohansenminiatures.com/15mm.htm), with loveable Lizardmen and "Bearmen" who can very easily be painted as Aslan.
And sixth, there is Critical Mass Games (http://www.criticalmassgames.com/) who, in addition to the quasi-Vargar Protolene, have a wide range of suited/power-armoured troops, miscellaneous aliens, walkers and grav vehicles.
Hope this helps!