[Kitters]

  I'm guessing you're not allowed to load music onto the workstation? Then yeah Cowon Z2 might be the best option if you don't want to get into trouble.
 
Otherwise, Fiio E-18 would be a good option as it can work both as a USB DAC on PC or as a standalone amp. Just plug it onto your workstation and play away and outside of office it doubles as a power bank or amp for your Galaxy S5. Win-win-win if you ask me.

 
I am definitely not allowed to do that, lol. If I got the E-18, it would be attached to my phone. The power bank feature is really attractive too. Now to just look at the prices for all three of these things and compare, lol. 

 

[cjs001]

   
I am definitely not allowed to do that, lol. If I got the E-18, it would be attached to my phone. The power bank feature is really attractive too. Now to just look at the prices for all three of these things and compare, lol. 

All the best.

 

[Kitters]

  All the best.

 
Much appreciated.

 

[batteraziiz]

   
I am definitely not allowed to do that, lol. If I got the E-18, it would be attached to my phone. The power bank feature is really attractive too. Now to just look at the prices for all three of these things and compare, lol. 

Have you considered just a cell phone in your pocket or desk streaming music to a bluetooth speaker of some sort?

 

[Berkovajazz]

Also there are Samsung Galaxy Players (yp-g, they have wi-fi, slot), very good sound and they are about 100-200$. 

 

[cjs001]

@Kitters If you have the patience, perhaps you could wait for these.