I have some money in an Individual (Solo) 401k plan, and I'm now
intent on investing it in one or more Bear Funds.

My plan (Enterprise Funds) doesn't offer any Bear Funds.
 
I'm therefore seeking any other Solo/Indivividual-K providers that do
offer short funds (like RYURX, USPIX, POTSX, BEARX, GRZZX, RSCOX,
etc.)

Fidelity Investments offers a self-employed 401(k) that is available
to sole proprietors.  Through its FundsNetwork®, you can invest in
four of the six ticker symbols in which you indicated interest (RYURX 
USPIX  GRZZX  BEARX).

I hope this meets your needs.  Fidelity will work with you to transfer
assets from your other plan to make it as easy as possible for you.

Sincerely,

Wonko

Sources:

"Fidelity Self-Employed 401(k) is available to self-employed
individuals or business owners with no employees other than a spouse,
including sole proprietors, partnerships, corporations, and "S"
corporations."

"No Fee* and A Wide Range of Investment Choices

Fidelity-managed mutual funds and 4,500 mutual funds from other
well-known fund companies through Fidelity FundsNetwork®, in addition
to individual securities, including stocks and bonds, CDs, and U.S.
Treasury bills."

"About Self-Employed 401(k)s" Fidelity Investments (2006)
http://personal.fidelity.com/products/funds/content/fn_overview.shtml.cvsr?refpr=ipmf3

4 Funds Comparison  
  RYURX  USPIX  GRZZX  BEARX     
Fund Name Rydex Inverse S&P 500 Inv CL UltraShort OTC ProFund Investor
CL Leuthold Grizzly Short Prudent Bear
General Information Trade Trade Trade Trade   
  Investment Objective Growth Growth Asset Allocation Growth   
  Morningstar Category Bear Market Bear Market Bear Market Bear Market   
  Assets ($M) 398.50  167.00  110.30  540.40    
  Morningstar Overall Rating -- -- -- --   
  Overall # In Category -- -- -- --   
Performance           
  Non-Load Adj. Returns           
    YTD 0.24  10.65  -1.88  10.93     
    1 Yr -2.48  -0.12  -10.19  15.99     
    3 Yr -8.40  -20.26  -13.45  0.11     

http://content.members.fidelity.com/mfl/compare_frame/1,,RYURX+USPIX+GRZZX+BEARX,00.html
    5 Yr -1.83  -14.87  -5.76  9.49     
    10 Year/Life? -5.06  -36.02?  -0.21?  -0.70    
  Load Adj. Returns           
    YTD --  --  --  --     
    1 Yr --  --  --  --     
    3 Yr --  --  --  --     
    5 Yr --  --  --  --     
    10 Year/Life? --  --  --  --    
Expenses           
  Expense Ratio 1.38  1.41  1.77  1.85    
  Turnover Rate % --  1257  0.0  129    
  Transaction Fee No No No No   
Volatility Measures           
  Beta -0.98  -3.28  -1.29  -0.58    
  R2 1.00  0.76  0.80  0.29    
  Standard Deviation 7.76  29.39  11.27  8.51    
 
 
 
* Closed to new investors.
** Closed to all investors.   
Need Help Selecting a Fund? Call 800-FIDELITY. 
 
 
"Compare Funds" Fidelity Investments (May 31, 2006)
http://content.members.fidelity.com/mfl/compare_frame/1,,RYURX+USPIX+GRZZX+BEARX,00.html